This invention relates to appliances for medical treatment and, more particularly, to an appliance collapsible for insertion into a human organ and capable of resilient restoration (which will be referred to as xe2x80x9cthe appliance to be implantedxe2x80x9d in this specification and claims), to a method of collapsing the appliance to be implanted, and to a device for introducing the collapsed appliance to be implanted into a catheter.
The artificial blood vessel is an example of the appliance to be implanted. At present, treatment of, for example, aortic aneurysm is conducted by implanting an artificial blood vessel. In particular, the portion of a blood vessel which has an aneurysm is removed by resection, and an artificial blood vessel is implanted in place of the resected portion and connected to the remaining blood vessel by suturing or the like.
The above-mentioned method of surgically implanting artificial blood vessels for treatment of aortic aneurysm, however, is highly dangerous. Especially, an emergency operation for treatment of a ruptured aneurysm has a low life-saving rate, and an operation of dissecting aortic aneurysm is difficult to conduct and has a high death rate.
Therefore, in order to treat these diseases without a surgical operation, a method has been developed of introducing into a catheter an appliance such as an artificial blood vessel in collapsed condition into a human organ such as a blood vessel, and transporting the appliance to a desired position such as an affected or constricted portion thereof, where the appliance is released so as to be expanded and implanted there with accuracy.
The appliance to be implanted comprises a pair of end wire rings and a frame mainly composed of connecting wires which connect the above-mentioned end wire rings. The appliance is pushed at the rear end wire ring into a catheter and transported to a desired organ in a human body. In order to transport the appliance, the force applied to the rear end wire ring should be transmitted to the front end wire ring. Therefore, it is indispensable that the frame should be made of comparatively strong metal and that the appliance should have the frame as an inevitable constructing element. If the above-mentioned frame is used, interference is likely to take place between the end wire rings and the frame and prevents the end wire rings from being folded, which makes it difficult to fold the end wire rings into a regular wavy shape. The difficulty in folding the end wire rings will make it difficult to collapse the whole appliance to be implanted into a small size.
As the end wire rings have an elastic limit, if a force exceeding the elastic limit is applied to the rings, the end wire rings folded for insertion into a catheter suffer plastic deformation so that the end wire rings may not be restored to a proper shape when released at an objective position in a human organ. The distortions caused by the plastic deformation may give rise to sliding resistance and prevent the appliance to be implanted from traveling in a catheter, thereby to make it difficult or impossible for the appliance to be transported to a desired position.
In addition, a frame, if used in the appliance to be implanted, is likely to hinder the appliance from being implanted in an appropriate shape into a human organ. Especially, in placing the appliance into a bent portion of a human organ, the frame may be deformed into a flat shape because different parts of the frame interfere with each other. Even if the appliance has been implanted, it may not be able to function as it is intended to. In the conventional frame, the wire of the wire rings provided at the opposite ends of the frame is exposed, so that the inner wall of a human organ may be scratched and damaged by the wire and blood is likely to leak out from the end wire rings because the rings are not adhered closely to the inner wall of the human organ.
Even though a check valve is provided at the outer end of a catheter whose front end has been inserted into the blood vessel of a human body beforehand, the check valve must be temporarily opened when the collapsed appliance is introduced into the catheter, thereby to cause a lot of bleeding. It is therefore desirable to provide means for preventing bleeding.
The present invention has been accomplished to solve the above-mentioned problems. The object of the invention is to develop an appliance of non-frame type, which can solve all of the above-mentioned problems.
The method of collapsing the appliance to be implanted in accordance with the invention is characterized by that the appliance to be implanted comprises a pair of discrete end wire rings, a tubular cover made of a sheet of flexible, tensile material which connects the above-mentioned end wire rings, and a plurality of intermediate wire rings arranged spaced apart between the above-mentioned end wire rings and circumferentially fixed to the above-mentioned cover by suturing or with adhesive; and that the method comprises the steps of: pulling forward the front end wire ring at a plurality of dividing points which equally divide the circumference of the front end wire ring while restraining the midpoints between each adjacent two dividing points by a tapered surface from moving forward following the forward movement of the dividing points, thereby to fold the front end wire ring into a wavy shape with the dividing points forming forwardly directed peaks and the midpoints forming the bottoms of forwardly directed valleys, and pulling the dividing points of the front wire ring farther forward thereby to fold the intermediate wire rings and the rear end wire ring into a wavy shape having the same phase as that of the front end wire ring by the effect of restraint with the tapered surface.
A loop for a pull string to be passed through may be formed at each of the dividing points on the front end wire ring so that a front pull string may be passed through each of the loops and pulled forward. In particular, a common pull string may advantageously be passed through a plurality of loops so that the dividing points may be gathered together by pulling the common front pull string. A funneled guide tube whose bore diameter is gradually reduced toward its forward end may be used to gather the dividing points and the midpoints by pulling forward the dividing points on the front end wire ring of the appliance to be implanted inserted into the funneled guide tube through its rear opening. In particular, resiliently deformable projections can be formed on the tapered inner surface of the funneled guide tube so as to bring the midpoints into contact with the projections thereby to effectively restrain the midpoints from moving forward following the movement of the dividing points and cause the midpoints to approach to each other. The end wire rings can be circumferentially covered with elastic protective material.
The appliance to be implanted in accordance with the invention is characterized by a pair of discrete end wire rings which are resiliently foldable and provided at opposite ends; that the end wire rings are connected by only a tubular cover made of a sheet of flexible, tensile material; and that a plurality of intermediate wire rings are arranged between the above-mentioned end wire rings and fixed to the above-mentioned cover at appropriate points on the circumference thereof by suturing or with adhesive.
The flexible, tensile sheet may be made, for example, of warps extending in the axial direction of the appliance to be implanted woven with wefts extending in the circumferential direction thereof. The warps are made of mono-filament of polyester capable of keeping its shape and the wefts are made of multi-filament of polyester having waterproofness.
The tubular cover may be in the form of bellows. Especially, the end wire rings may advantageously be connected by restraining strings so as to prevent the bellows from overstretching to exceed a given limit. The end wire rings can be circumferentially covered with an elastic protective material. Further, thorns can be provided on the circumference of at least one of the wire rings so as to stick into a human organ to be embedded therein. The thorns may be effectively formed by curving a wire into a loop, crossing the opposite end portions of the wire, and fixing the crossing point, thereby to form the opposite end portions into the thorns.
The device for introducing the appliance to be implanted in a collapsed state into a catheter in accordance with the invention comprises an attachment having a flexible check valve which closes an open end thereof and fixed to an open end of a catheter, and a cartridge removably attachable to the above-mentioned attachment and having an open end closed by a flexible check valve and a front end portion connected to the above-mentioned catheter when the cartridge is attached to the attachment; and by that the check valve of the cartridge is pushed open to introduce the appliance to be implanted into the cartridge, and while the check valve of the cartridge is kept nearly closed, the front end portion of the cartridge is inserted into the catheter by pushing the check valve of the attachment open.
The bore diameter of the attachment of the catheter is made larger than that of the open end of the catheter, so that when the cartridge is attached, the bore of the front end portion of the cartridge may be smoothly connected to the open end of the catheter through the attachment of the catheter.
With the method of collapsing the appliance to be implanted in accordance with the invention, the operation of collapsing the appliance can be conducted with ease and accuracy. It is difficult to fold the front end wire ring into such a small size that can be contained in a catheter just by applying non-directional external force thereto. However, if the dividing points which equally divide the circumference of the front end wire ring are pulled forward with the midpoints provided between the dividing points being restrained by a tapered surface from moving forward following the dividing points, the front end wire ring is folded into a wavy shape with the midpoints serving as footholds and with the dividing points forming forwardly directed peaks and the midpoints forming the bottoms of forwardly directed valleys. After the front end wire ring has been bent, the intermediate and the rear end wire rings also are folded into a wavy shape having the same phase as that of the front end wire ring by pulling farther forward the dividing points on the front end wire ring to transmit the pulling force to the intermediate and the rear end wire rings through the tensile cover, and by simultaneously restraining the intermediate and the rear end wire rings by means of a tapered surface, thereby to collapse the whole appliance into a small size with ease.
What should especially be referred to is that the method of collapsing the appliance to be implanted in accordance with the invention is characterized by that a pair of end wire rings provided at the opposite ends of the appliance are connected by only a tubular cover which is made of a sheet of flexible, tensile material; and that the front end wire ring is pulled forward. The conventional method, in which the rear end portion of the appliance to be implanted is pushed to insert the appliance into a human organ, requires a relatively strong frame made mainly of connecting wire rings in order to transmit the force applied to the rear end of the appliance to the forward portion thereof. However, the invention is based on pulling the front end wire ring forward, thereby to make it possible to insert the appliance with ease even without a frame. In addition, the cover follows the movement of the wire rings being folded and is transformed into any desired shape, thereby to avoid interference between the wire rings and the frame. Consequently, by the method of collapsing the appliance in accordance with this invention it is possible to fold each of the wire rings into a wavy shape and to collapse the whole appliance into a small size with ease.
The operation of folding the wire rings is conducted with ease by forming loops for a pull string to be passed through at the dividing points on the front end wire ring and pulling forward a front pull string passed through the loops. In particular, a common front pull string passed through a plurality of loops is more effective to change the pulling force to a force to fold the wire rings because the dividing points are gathered toward each other.
In collapsing the appliance, a funneled guide tube whose bore diameter is gradually reduced in the forward direction may advantageously be used, so that the dividing points and midpoints of the wire rings are gathered toward each other as the appliance to be implanted is inserted farther into the funneled tube, thereby to collapse the appliance as a whole into a small size. If projections resiliently deformable and engageable with the midpoints are formed on the tapered inner surface of the funneled guide tube, the midpoints are urged toward each other by the counterforce from the projections, and a space is formed between the end wire rings and the funneled guide tube, thereby effectively to prevent the appliance and the funneled guide tube from closely contacting each other to increase sliding resistance therebetween so that the appliance cannot be moved in the guide tube.
Elastic protective material circumferentially covering the end wire rings is useful to prevent the appliance from being damaged when collapsed into a small size. If the wire ring is bent to such a degree that the elastic limit is exceeded, not only does it becomes difficult for the ring to be restored to its original annular shape but also it becomes impossible to move the ring in a catheter due to the bent portion being caught in the catheter. However, if protective material is provided, the material disperses the tension which would otherwise be exerted locally on the dividing points when the points are strongly pulled, thereby to prevent tension from being applied locally to the dividing points so that the elastic limit is exceeded to bend the wire ring. The protective material prevents the front end wire ring from being plastically deformed, and provides it with a proper capability of resilient restoration to an annular shape and of traveling smoothly in a catheter, thereby to fold the front end wire ring into a regular wavy form.
The appliance having no frame, as mentioned above, properly functions as an artificial blood vessel. The appliance in accordance with the invention has a feature that the cover itself is tensile and is held by the wire rings at both ends and the intermediate wire rings at appropriate points thereof Therefore, when the whole appliance is released from the state of being collapsed and each of the wire rings are resiliently restored to the annular shape, the cover is resiliently restored to its original proper tubular shape. The conventional appliance having a frame is likely to be deformed flatly because of mutual interference of the component parts when it is arranged in a bent portion of a human organ. However, the appliance of the invention having no frame can be transformed into any desired shape so as to conform to different shapes of a human organ.
A sheet woven with warps and wefts, in which the warps are made of monofilament of polyester and the wefts are of multi-filament of polyester, makes the whole appliance flexible. In addition, the warps provide the cover of the appliance with tensile strength in the axial direction and a capability of keeping its shape, and the wefts make the sheet closely woven and increase its waterproofness.
If the sheet of the cover is in the form of bellows, the whole appliance is bent smoothly, thereby to improve the condition of the appliance when implanted into a human organ. If the sheet of the cover is in the form of bellows, restraining strings connecting the front and the rear end wire rings can prevent the bellows from stretching to such a degree that the elastic limit is exceeded to be flat.
The elastic protective material circumferentially covering the wire rings can prevent, as mentioned previously, not only the wire rings from being plastically deformed when folded into a small size but also the inner wall of a human organ from being damaged by direct contact with the wire rings. The protective material also acts as a seal to attach both ends of the appliance to be implanted tightly to the inner wall of a human body, thereby to effectively prevent leakage of blood through the ends of the appliance when implanted.
When thorns are provided projecting from the wire rings, they stick into the inner wall of a human organ to be embedded therein so that the whole appliance is fixed to the human organ. Therefore, the thorns effectively prevent the appliance from being displaced or even carried by blood flow downstream in a blood vessel. The thorns are formed with ease by curving a wire into a loop, crossing both end portions of the wire, and fixing the crossed parts with a string or the like, even though the material of the wire is difficult to weld. The thorns thus formed reliably function as mentioned above for a long time.
In addition, with the device for introducing a collapsed appliance to be implanted into a catheter in accordance with the invention it is possible to introduce the appliance to be implanted smoothly into a catheter. In particular, the appliance to be implanted is inserted into the cartridge by pushing the check valve open as far as the appliance reaches a position at which it is almost completely contained in the cartridge. Before or after the insertion, the cartridge is attached to the attachment provided at the open end of the catheter, and then the appliance is pulled farther forward in that condition so as to be introduced into the catheter through the attachment. When the check valve in the attachment is opened, the check valve of the cartridge is closed, so that blood flowing into the cartridge is prevented from flowing outside the body through the cartridge without fail. In addition, if the appliance is to be inserted directly into the catheter, the appliance cannot be inserted smoothly because of the catheter and the appliance being flexible, and the catheter is bent by the force applied to the appliance, thereby to block the passage through which the appliance is to be inserted or to make the catheter fragile. On the other hand, if the appliance is to be inserted into the catheter through the attachment and the cartridge, by making the attachment and the cartridge strong and of such a shape as to be handled with ease it is possible to solve the problem of the catheter being bent or otherwise deformed, thereby to enable the appliance to be introduced into the catheter smoothly and with ease. If the bore diameter of the attachment is made bigger than that of the catheter and the bore diameter of the front end of the cartridge is smoothly connected to that of the open end of the catheter when the cartridge is attached to the catheter, it is possible to prevent the appliance to be implanted from being temporarily swollen in the attachment and caught therein, and to introduce the appliance to be implanted deep into the catheter.